JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
  <div class="dates">
    <div class="dates-item">19.08</div>
    <div class="dates-item">20.08</div>
    <div class="dates-item">21.08</div>
  </div>
  
  <div class="block">
    <div class="flex-row">
      <div class="box">15</div>
      <div class="box">18</div>
      <div class="box">20</div>
    </div>
    <div class="flex-row">
      <div class="box">9</div>
      <div class="box">5</div>
      <div class="box">7</div>
    </div>
  </div>
  
  <div class="lines">
    <div class="blue"></div>
  </div>
</div>

SCSS

.main{
  display: flex;
  flex-direction: column;
  position: relative;
  background: yellow;
  width: 140px;
  height: 100px;
  .dates{
    display: flex;
      &-item{
        margin-left: 15px;
        &:nth-child(1){
          margin:0;
        }
      }
    }
    .block{
      display: flex;
      flex-direction: column;
      margin-top: 10px;
      .flex-row{
        display: flex;
        .box{
          width: 45px;
          text-align: center;
          border: 1px solid red;
        }
      }
     }
     .lines{
       position: absolute;
       .blue{
          position: absolute;
          top: 28px;
          left: 48px;
          width: 45px;
          height: 40px;
          background: blue;
       }
     }
}